On orbit 48, after 75 hours of flight a problem arose. During a pass over the continental US the flight computer was updated. McDivitt was told to switch off the computer. He flipped the switch but the computer did not turn off. On the ground at mission control, efforts to solve the problem began immediately. For the next few orbits, the crew received instructions for trying different switch positions, after all the switching the computer finally failed entirely and could not be turned back on. Now the astronauts would have to resort to a rolling Mercury-type reentry, rather than the lifting bank angle the computer was supposed to help them achieve…

For the first time Television coverage of the launch had an international audience, as the scene was broadcast to 12 European nations via Intelsat 1 aka the Early Bird satellite of episode 59. Heightened by the prospect of an EVA and the first use of the new Mission Control Center in Houston, interest in Gemini IV reached levels never again matched in the Gemini program…

Mercury-Redstone 4 was the fourth mission in the Mercury-Redstone series and the second U.S. manned suborbital spaceflight. The mission was essentially a repeat of Alan Shepard’s Freedom 7 flight. So why was it necessary to launch another sub-orbital mission? Why not proceed with an orbital flight to match the Soviet Vostok 1? Among other things the U.S. needed more space experience to corroborate the “Man-in-Space” concept. Also the Redstone was the only booster NASA had that was approved for manned launches. The Atlas booster was available but not ready. Atlas was capable of putting a Mercury Capsule into orbit, but it had been launched three times with unmanned capsules, and it had exploded on 2 of the 3 attempts.